1. Field of the Invention
The present invention relates to an agent for increasing brown fat, comprising a conjugated linoleic acid as an active ingredient. More particularly, the present invention relates to an agent for increasing brown fat, comprising a conjugated linoleic acid as an active ingredient, which agent can increase brown fat cells capable of consuming extra energy and producing heat to prevent obesity, and use of the agent in the field of foods.
2. Background Art
In recent years, patients suffering from obesity have been increased also in Japan, and this is becoming a serious social problem. Obesity derived from such factors as increased ingestion (hyperphagia), reduced excercise (lack of excercise), and a fluctuation in generation of body heat causes accumulation of a large amount of body fat. This is causative of arteriosclerosis, hypertension, diabetes, and cardiac diseases, and, in some cases, leads to complications, such as angiopathy, neuropathy, and aphylaxis.
Fat is stored in adipose tissues. Adipose tissues are classified into two types which are utterly different from each other in function. One of the adipose tissues is a white adipose tissue which occupies the major part of the adipose tissues and functions to accumulate extra energy, and the other adipose tissue is a brown adipose tissue which has a function opposite to that of the white adipose tissue, that is, functions to consume extra energy. The brown adipose tissue is significantly found in infancy, and the level thereof decreases with aging. The brown adipose tissue is present in the back of the neck, a portion around shoulder blade in the back, axilla, periphery of the heart, and periphery of the kidney, and the total weight thereof is as small as about 40 g. This brown adipose tissue is governed by a sympathetic nervous system, and functions to generate heat for body temperature retention purposes and, in addition, to burn extra energy, thereby preventing obesity. Increasing and developing this brown adipose tissue are a great aid in eliminating obesity and are expected to prevent or reduce obesity.
On the other hand, conjugated linoleic acids are isolated from fried meats (Y. L. Ha et al., Carcinogenesis, 8, 1881-1887, 1987), and, up to now, the following reports have been made on various activities of the conjugated linoleic acids: {circle around (1)} anti-carcinogens (Cancer Research, 51, 6118-6124, 1991); {circle around (2)} method for enhancing animal feed efficiency (Japanese Patent No. 2745245); {circle around (3)} method for storing foods and a preservative for use therein (Japanese Patent No. 1935402); {circle around (4)} methods for preventing weight loss, reduction in weight gain, and anorexia due to immune stimulation (U.S. Pat. No. 5,430,066); {circle around (5)} method for reducing body fat (U.S. Pat. No. 5,554,646); {circle around (6)} methods for maintaining and enhancing bone mineral content (U.S. Pat. No. 5,804,210); and {circle around (7)} method for reducing secretion of apolipoprotein B (U.S. Pat. No. 5,837,733). So far as the present inventors know, however, there is no report such that the conjugated linoleic acids act to increase brown fat.
Accordingly, it is an object of the present invention to provide pharmaceutical preparations, foods, and feed which can increase and develop brown adipose tissues to prevent and remedy obesity.
The present inventors have repeated extensive and intensive studies using brown adipose tissues as an index of the usefulness in prophylaxis and therapy of obesity and, as a result, have found that conjugated linoleic acids have high activity to increase brown fat and thus are useful for the prophylaxis of obesity. This has led to the completion of the present invention.
Thus, according to the present invention, there is provided an agent for increasing brown fat, comprising a conjugated linoleic acid as an active ingredient.